A multi Wide Area Network (WAN) Site-to-Site VPN router is a router that supports aggregating the bandwidth of multiple interconnections, e.g., WAN connections for accessing one or more remote private networks. In some implementations, each TCP/IP session is routed to only one WAN. In this configuration, a single TCP file transfer session can only utilize the bandwidth of one WAN connection on each end. For example, in a session based site-to-site virtual private network (VPN) connection VPN traffic is routed to multiple WAN connections between two sites (e.g., sites A and B).
In one implementation, M×N tunnels are initially formed between the WAN connections where M and N are the number of WAN network connections of site A and site B, respectively. Application TCP/IP sessions are then routed over the different tunnels. It is notable, however, that while a session based site-to-site VPN is able to utilize different tunnels for different sessions, a single download session in this type of connection is only able to utilize one tunnel.
When there is packet loss or packet drop in a data session between two routers, there may be various ways to recover the lost packets. It is common that the sender router resends dropped or lost data packets until the receiving router receives the data packets and sends corresponding acknowledgement. However, this may consume bandwidth and increase network congestion. Higher network congestion may result into more packet drop. Therefore, a solution is required such that the dropped or lost packets may be recovered without the sending device resending the data packets.